Effects of cowpea varietal susceptibility and low pressure on the mortality of life stages of Callosobruchus maculatus (Coleoptera: Bruchidae)

Low pressure creates a low-oxygen controlled atmosphere that can kill all developmental stages of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae). This study investigated the interaction of low pressure with seed variety to determine the susceptibility of different cowpea varieties to developmental stages of C. maculatus. Laboratory studies were performed to determine exposure periods to low pressure (32.5 ± 1.0 mm Hg) necessary to kill all life stages of C. maculatus on different cowpea varieties. The results indicated that with the exception of eggs, differences in exposure periods required to achieve 100% mortality varied with life stage and variety. The larval stages were the most susceptible, and larvae required shorter exposure periods to low pressure when reared on C. maculatus resistant varieties (24-125B-3 and IT89KD-288) than on susceptible varieties (CB-3, CB-5, CB-46 and UC-27). Analysis of variance (ANOVA) showed a significant interaction between the life stages of C. maculatus, exposure time and cowpea varieties on mortality. Integration of low pressure applications with storage of cowpea varieties resistant to C. maculatus has the potential of providing an alternative pest management tool to fumigants, which are sometimes used in protecting cowpea in storage from infestation by C. maculatus.